In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.
Today, advanced antenna setups and techniques enable an ever increasing throughput and robustness in wireless communications networks. One such technique is to shape the beams (i.e., to perform beamforming) of the antenna array. Beamforming is today made possible with the use of so-called reconfigurable antenna systems (RAS).
A cell specific beam refers to the antenna beam pattern generated to provide the cell specific reference symbols (CRS) coverage for a cell in the communications network. This beam pattern will be similar to all the wireless devices served in the cell. In general terms, the coverage area of the cell can be largely adjusted by changing the parameters related to cell specific beamforming. In general terms, the cell shape is determined by the coverage of the CRS. CRS are transmitted in particular time-frequency slots. In general terms, the shape of the beam (i.e., the beam shape) is controlled by combining antenna elements in a phased antenna array.
Cell specific beams are considered when deciding the coverage area of the cell and also when defining the distribution of the received signal strength in the coverage area of the cell. The cell specific beams can be controlled by changing the antenna parameters such as antenna downtilt, azimuth orientation, elevation and horizontal beam widths.
Device specific beamforming is a way to improve the path gain towards the served wireless devices by providing directive antenna gain towards the wireless devices. In general terms, device specific beams are more narrow in beam width than the cell specific beam so as to maximize the antenna gain towards the wireless device. A network node of a single cell can serve multiple of its served wireless devices with multiple such device specific beams. That is, within the coverage area of a single cell specific beam, there can be one or more device specific beams active at the same time.
In general terms, a self-organizing Network (SON) is an automation technology designed to make the planning, configuration, management, optimization and healing of communications network simpler and faster. The SON functions in the network may thus be configured to automatically change network related parameters to improve the performance of the communications network. Such SON functions may include antenna parameter optimization, load balancing, etc. In case of antenna parameter optimization, the antenna parameters may be changed either to reduce the interference to neighbor cells and/or to improve the signal strength to wireless devices in the same cell and/or to perform load balancing between cells. This is generally referred to as a cell shaping SON functionality.
There are many ways to carry out load balancing, such as cell shaping or mobility load balancing, by introducing cell range expansion etc. Each of these load balancing mechanisms are beneficial in different scenarios.
When cell shaping needs to be carried out in a cell, existing mechanisms as disclosed above are based on either jointly optimize performance at the borders of a cell with one or more neighbor cells, or individually optimizing the performance in the cell alone. While performing the changes in the cell for which performance is to be optimized, or while trying to understand with which neighbor cell(s) the cell for which performance is to be optimized needs to be jointly optimized, existing mechanisms may rely on different additional measurements, which cause measurement overhead. Alternatively, existing mechanisms perform the antenna parameter changes and then analyzes the impact of these changes on the system performance (such as the overall performance of the communications network, or part thereof) in order to determine whether the performed changes were beneficial or not. The first approach introduces additional signaling overhead. The second approach is prone to selection of poor antenna parameters and/or poor identification of neighbor cell(s) for joint optimization, thereby causing performance dips (possibly in coverage and/or capacity of the cell).
Hence, there is still a need for an improved cell shaping for load balancing and/or radiation beam pattern change.